食管癌放疗中左心室肌剂量体积指标评估误差研究

Analysis of the evaluation errors of dose-volume parameters for left ventricular myocardium in esophageal cancer radiotherapy

目的 评估食管癌放疗中左心室肌剂量体积指标随心跳的动态变化范围.方法 选取22例患者的屏气下心电门控4DCT,在其20个时相（0％ ～95％）上分别勾画左心室肌.在模拟定位CT上进行计划设计,将剂量分布导入MIM Maestro系统,重建4D剂量体积直方图.分析不同时相左心室肌的位置、体积及相似性指数（DSC）变化;研究不同时相下左心室肌Dmean、V10、V20、V30及V40的变化范围.结果 （1）左心室肌在y轴方向位移最大;不同时相间体积及DSC最大变化率分别为（24.23±11.35）％ 和（184.33±128.61）％（P〈0.05）.（2）左心室肌不同时时相Dmean最大变化率为（87.05±38.34）％,最高可达163.52％（P〈0.05）.（3）左心室肌V10、V20、V30及V40的最大差值分别为（13.64±4.33）％、（12.84±4.55）％、（11.62±4.85）％及（3.63±2.56）％（P〈0.05）.结论 食管癌放疗中,心跳对左心室肌剂量体积指标的影响不容忽视,传统基于静态 3DCT 对左心室肌进行剂量体积评估时存在较大误差,可能是导致剂量体积指标对放射性心脏损伤预测效能较低的主要原因。

Objective To evaluate the dynamic variation of the dose-volume parameters of the left ventricular myocardium following heart beat in radiotherapy for esophageal cancer. Methods The left ventricular myocardium of 22 patients was contoured on 20 phases （0%-95%） of electrocardiography （ECG） gated heart 4DCT images. The radiotherapy plan was designed on the simulation CT images,and then the dose distribution of radiotherapy plan was imported into MIM Maestro system and 4D dose-volume histogram （DVH） was reconstructed. The variations of position,volume and dice similarity coefficient （DSC） of the left ventricular myocardium were analyzed. The changing ranges of Dmean ,V10,V20 ,V30 and V40 of the left ventricular myocardium during different phases were statistically compared. Results （ 1 ） The biggest displacement of the left ventricular myocardium was in Y axes. The maximum variation rate of volume and DSC of the left ventricular myocardium were （24.23±11. 35）% and （184.33±128. 61）% in different phases with statistical significance （both P〈0. 05）.（2） The maximum variation rate of Dmean of the left ventricular myocardium was （87.05± 38. 34）% in different phases with the highest rate of 163. 52% with statistical significance （P〈0. 05）.（3） The maximum variation values of V10,V20,V30 and V40 of the left ventricular myocardium were （13.64±4. 33）%,（12.84±4. 55）%,（11.62±4. 85）% and （3.63±2. 56）% with statistical significance （all P〈0. 05）. Conclusions The impact of heart beat on the dose-volume parameters of the left ventricular myocardium should be considered during esophageal cancer radiotherapy. Traditional static 3DCT-based assessment of the dose-volume parameters of the left ventricular myocardium can yield relatively large errors, which is probably reduces the prediction efficiency of the dose-volume parameters for radiation-induced heart injury.